1. Technical Field
The present invention relates to apparatus for determining the blood erythrosedimentation (ESR) of a plurality of blood samples, and for similar sedimentation tests on other liquids.
2. Prior Art
It has long been known that the erythrocytes present in the blood of subjects suffering from various diseases sediment more quickly. The increase of the blood erythrosedimentation rate (ESR) is due essentially to alterations of the plasmatic and erythrocytic factors intervening, which promote the formation of rouleaux.
The traditional method of measurement of the blood ESR is Westergren's. 4 ml of venous blood is mixed with 1 ml of anti-coagulant (a 3.1% solution of sodium citrate). A pipette (for example a glass pipette, 30 cm long and gauged in millimeters from 0 to 200) is filled by suction exactly to the mark 0, and then it is mounted on a suitable pipette holder in a perfectly vertical position. It is left at ambient temperature for 60 minutes, after which the result is read off (1st hour). The distance in millimetres between the plasmatic meniscus and the erythrocyte one represents the value of the erythrocyte sedimentation rate (ESR). The reading may be repeated after a further 60 minutes (2nd hour).
Another method is that described by Wintrobe in which use is made of a hematocrit tube. In this method also the results are expressed in millimetres per hour. A number of variations have been introduced into these methods; among the most important of these mention may be made of micro-methods and sedimentation in a pipette inclined at 45.degree. to accelerate ESR and reduce reading times.
All the methods mentioned above exhibit a number of drawbacks. These methods, though they can be simply followed commit for a not unappreciable time the laboratory technician who has to carry out a fairly substantial number of examinations. In addition, in the course of handling, as the pipettes are filled by suction with the mouth, there occur for the operator serious possibilities of coming into direct contact with samples of infected blood.
In addition there are the following possibilities of errors:
(1) if the exact concentration of anti-coagulant in the blood is greater than anticipated, this reduces the ESR; PA0 (2) If the pipette is not clean and contains traces of detergents, alcohol, ether or other compounds this affects the results; PA0 (4) If the temperature is not around 20.degree. C. or not higher than 27.degree. C. this may affect the results and, in addition, the exposure of pipettes to the sun's rays affects the results; PA0 (5) If the reading is not made at the correct time the result will be affected; PA0 (6) If the supporting plane is subject to vibration or movement this alters readings; PA0 (7) Errors also occur both during the pipette filling stage (using one sample for another, imprecise resetting) and during reading off and manually transcribing the data.
(3) If the pipette is not completely vertical this introduces errors, for example an inclination of only 30.degree. from the vertical may accelerate ESR by 30%;